Fluid system pressure booster



Nov. 28, 1944. J. HULMAN `x-:rAL 2,353,528 l ELUID SYSTEM PRESSUREBOOSTER Filed Sept.` 4, 1942v 2 Sheets-Sheet `1 du; u s HUA M4N J.HULMAN I'AL FLUID SYSTEM PRESSURE BOOSTER LNw, 2s, 1944.

2 Sheets-Sheet 2 Filed Sept. 4, 1942 lie EAM/4N drawings, wherein:

f Patented Nev. 2s, 1944 -UNITEDI STATE s PATENT FLUID SYSTEM PRESSUREBOOSTER V l `Julius Hulman and Bernard Beaman, y

f 2,363,523 OFFICE Dayton, Ohio Original application August 6, 1941,-Serial No. 405,673. Divided and bthis application September 4, 1942,Serial No. 457,300 `A 3 Claims. (.Cl. 103-5) (Granted under the act ofMarch 3,1883, as amended April 30, 1928; 370 0. G. 757,)

The invention described herein may be manufactured and used by or forthe Government for governmental purposes, without the payment to us ofany royalty thereon.

This invention is a division of our co-pending application Ser. No.405,673, iledAug. v6, 1941, patented Dec. 8, 1942, No. 2,304,096, andrelates to pressure boosters, and is applicable to any uid Asystemwherein a iluid is moved against a resistance.

The resistance may comprise no more than the friction encountered by theiluidin ,moving `through the system, or it may include additionalresistance, b ut in any event somepressure or head creating means isrequired at some part of the system to maintain ilow.

Whatever the form that such pressure creating instrumentality may take,therewill be a difference in pressure, as between the upstream Aanddownstreamside thereof, in the system, such diiierence usually beinggreater as the resistanc to be overcome is higher.

Such pressure difference is, of course, a function of a iiuid system ofthis character, but there are many instances where the pressure drop onthe low side is so great as to be highly objectionable, such for exampleas when the suction head, due to lift or equivalent frictionalresistance, appreaches the stage Where a liquid cavitates at v the'suction side of a. pump. y

Figures 1 and 2 are diagrammatic illustrations included only tofacilitate description oi the principles of the invention.

Fig. 3 shows 4an application of the invention to at A-A; P2 the pressurewithin the pipe I0 meas'- ure'd at the tank connection as at -B-B; Psthe pressure within the tank I6; and P4 thepressure within the pipe lemeasured'downstream oi the tank connection as at C-C.

In Figure 2, which is a diagrammatic illustration of the apparatusFigure 1, but modiiled to illustrate the subject matter of theinvention, the

same pipe i0, tank I6, and conduit are used..

the pressures Pi, P2 and P'4 being taken at the same sections, namely, A-A, B-B and C-C.

The modiiication consists in removing a portion of thepipe I0 andreplacing it with a venturi 24, the tank I6 being connected by theconduit 20 int the throat of the venturi. Since the throat pressure P2and the tank pressure Ps are still the same as they are in thearrangement l Figure 1, the pressures Pi and P4 will 'be higher,

the fuel system of an internal combustion engine.

Fig. 4 is an axial section through the relief valve drawn to an enlargedscale.

In Figure 1, whichshows diagrammatically a portion of a conventionaliiuid system to which the improved features of this invention havenot`been applied, a pipe I0 contains a iiuid l2 moving in the directionindicated .by the arrow I4. A tankV i6, filled with the fluid to thelevel I8 is connected to the pipe I0 by a conduit 20. The l tank maypreferably be vented at 22.

In Figure 1Pi is the pressure Within the pipe Il measured upstream ofthe tank connection as this being aninherent function of a venturi whichis well understood.

In Figures 1. and 2 the tank I8 is shown as being vented to atmospherethrough the opening 22 but it will be obvious that this vent' may beconnected to a source of pressure which may be: above or belowatmospheric pressure.

Referring again to Figure 1, and Vassuming that there is no flow fromthe tank I6 to the pipe l0. Pz ,is equal to Ps plus the head orequivalent head of the fluid above the'pipe. A tank connection beingnecessary, it is made at the low pressure pointgin thesystem. If flow isin the direction of the arrow I4, Pi is greater than Pz and Pz isgreater than P4, the -pressureloss being due to the ow of duid in pipeI0. If the sections A-A and .C-C are at considerable distances apart,the pressure P4 may be considerably less than Pz.

This gradual pressure drop is a. function of a system of thischaracter., and must be compensated for, if circulationis to continue,by some form of pressure raising means, usually a pump. Under someconditions of operation this presents no diiriculty, being merely amatter ci providing a pumpof suiiicient capacity to raise the pressurelthe desired amount.

Under other. circumstanceshowever, the operating characteristics of -thepump are considerably aiected by` a low pressure P4 at the inlet side ofthe pump, as for instance when pumping at the pump inlet.

Referring now to Fig. 2, Pz is equal to P3 plus thefhead, just as itisin Figure 1 Fluid ilow through a venturi, however, results in anincrease in the velocity, and a consequent lowering of the pressure inthe Venturi throat, the'throat'pressure being always less than thepressure at points just before entering and after passing through theventuri. It Vfollows that, since the throat pressure Pz is the same inFigure 2 as in Figure l, the pressures P'i and P4 in Figure 2 arerespecf tively greater than the pressures Pi and. P4 in- Figure 1.Therefore by connecting a tank and feed pipe of a given pressure Pa intothe throat' of a lventuri 24, Figure 2, instead of directly into thepipe i0, Figure 1, all other points in the system, Figure' 2, have theirpressures raised an amount corresponding to the differences between thepressures Pi and P4 of Figure 1 and Pi and P'l of Figure 2.

'I'he foregoing description is intended to cover `the improved pressurebooster generally. However, with a view of more clearly describing theprinciples involved, and without intent to place' through the bypasscircuit 60T back to the inlet side 62'of the pump. Y.

. The circuit 60 includes a relief valve 64 having a spring 65 which isadjusted to the pressure required at the carburetor, and which bypassesfuel only after this pressure is exceeded, circulation throughthe bypasscircuit being in the direction of the'arrow 66. A venturi 68 and a pipeI complete the bypass circuit to return the excess fuel back to theinlet 62 of the pump.

' A lfuel tank 12 has a sump 14 from which fuel is taken by the pipeA1li which has its lower end connected into the throat 'lll of theventuri. A vent 80 connects the space above the fuel level .in tank 12to the atmosphere, although of course it may be connected to a source ofsuperor sub-atmospheric pressure, if desired. When conthrough a flexibleshaft 54. Pump of the pump 52 and the suction lift is thereforecorrespondingly less, and while the pump may not require suchassistancev when operating at sea level, where it will ordinarily runfull and without cavitation, yet for high altitude ying,

' the amount which a venturi arrangedas shown in the drawing may raisethe pressure at. the

pump inlet, where the fuel pressure in the system isordinarily lowest,and where boiling begins, will materially add to the altitude which maybe reached by aircraft equipped with this device. j

While one specific embodiment of the inven.-

tion has been shown and described,l and its superiority noted, it willbe apparent that the invention may be employed to good advantage insubstantially any circulating fluid system where it is desirable toraise the pressure on the low pressure side of the circuit, which willbeat the intake. of the pressure producing means. 'I'his pressure rise isaccomplished with little change in conventional practice and thenecessary addition includes no moving parts, nor does it add -to thepower required to operate the system.

Throughout the specification and-claims `we have used the word venturi,but it will Vbe understood that this term is to be construed in itsbroader sense to include any device having its passageway restricted to.one. part to cause increased rate of flow and a consequent loweredpressure in the restricted part.

So, also, theterm throati' when applied to a venturi or 'its equivalentshould be construed toy include any connection near enough to the throatto get the benefit of the increased iiow and lowered pressure.

We claim: 1..,In a fluid system; a pump, means contain.-

A. ing a continuous pressure tight'passageway connected 4to atmosphereas shown, the pressure at point 18 will of course be determined by theheight of the fuel level in the tank 12,'but due to the capacity of theventuri to raise the pressure at all points removed from the throat, the

pressure in all other parts of the circuit 60, which includesthepressure at the inlet side 62 of the pump 52, will be higher, the amountof pressureincrease being affected of course by the rate of flow, which'is in turn affected by the amount of surplus capacity of the pump.v

'I'he desirability of raising the pressure at the inlet side of the fuelpump, particularly offuel pumps for aircraft .engines,`is well known,4for -while no great difficulty is experienced at sea level in pumpingagainst the normal suction head 0f a system of this kind, the dimcultyis enormously increased at high altitudes rdue to the progressivelyloweredboiling point of the Vliu-- uid fuel as altitude increases.

The normal suction lift is, of course, influenced to some extent bythezheight of the pump above the level of the fuel in the tank, whichmay vary considerably due to pitch or bank of the,

aircraft and may also be infiuenced'by the size and length of thesuction'pipe, which is for that reason made of as large a diameter'andas thin a wall asis consistent with good practice. But even with `thisattention to design, the normal suction lift is considerable, so'thatany -device necting the suction and discharge sides of said pump, apressure responsive means in said passageway dividing it into a highpressure region between the pressure responsive means and the dischargeside, and a low pressure region between the pressure responsive meansand the suction side, a venturi included in the circuit in the lowpressure' regionfa receptacle, and a single conduit extending from thereceptacle and connectl' i'ng it to the throat 'of the venturi.

12. In a fluid system, a' pump, means containing a continuous pressuretight passageway conneeti'ng the suction and discharge sides of thepump, a spring loaded relief valve in said passageway, a venturi betweensaid valve and the' suction side of said pump, avessel, anda singleconduit extending from said vessel and connecting said vessel to thethroat of -the venturi.

which will lessen that lift is considered o'f great importance.V f v Inthe fuel system shown in Figure 3,- the venturi 68 raises the pressureat the inlet side 62 v3. For use in connection with a fuel system for aninternal combustion engine, which-system includes a carburetor, a fuelpump, a fuel tank and conduit means connecting the discharge side ofAthe pump to the carburetor, the improvement in said systemA whichcomprises a conduit means connecting the discharge side of the pumppressure tight to the suction side, said second conduit means includinga spring loaded relief valve and a venturi between said valve and thevsuctionside of said pump, and a single fuel conduit meansextending fromsaid tank andconnecting said tank to the throat of the venturi, wherebyall fuel flowing to said carburetor passes through the throat ofsaidventuri.

JUIJUSH'UIM AN. -BERNARD BEAMAN.

